Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Effective Income Tax Rate Reconciliation, Percent	35.90%	38.00%	33.90%	38.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount			$ 13,600
Income Tax Expense (Benefit)	$ 56,277	$ 67,067	154,499	$ 192,778
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	1,500
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	23,200		23,200
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	5,800		5,800
Other Noncurrent Liabilities [Member]
Unrecognized Tax Benefits	35,600		$ 35,600
Accounting Standards Update 2016-09 [Member]
Income Tax Expense (Benefit)	$ (4,500)